Chinook Roofing Blog

Metal Roofs: Common Causes of Leaks


Posted on: November 09, 2016

A metal roof during a rain storm.

Metal roofs are considered to be one of the most resilient and reliable roofing options available, but that doesn’t mean that they’re completely immune to problems, including leaks. If you’re experiencing a water leak in your metal roof, use the following four common causes of leaks to help you pinpoint the source of the trouble.

1. Misaligned Roofing Screws 

This is perhaps the most common cause for leaks in metal roofs. When a metal roof is installed, the screws are normally driven in with a rubber washer directly under the head of the screw to provide a watertight seal. Unfortunately, not every roofer pays attention to the finer details, which means that sometimes the screws can be crooked, overdriven or underdriven into the roofing panel. If the screws are crooked, the rubber washer doesn’t cover the entire area of the screw hole, allowing some space for water leakage. If the screws are overdriven, it can bust or bulge the washer, reducing its effectiveness; if they’re underdriven, the screw won’t sit well against the panel, and the watertight seal is never formed. If you’re experiencing a leaky roof, this is definitely one of the first details you should inspect.

2. Worn Sealants 

When a metal roof is installed, a metal roof sealant is used to create a weather-tight seal in order to protect the roof from damage due to water, wind, dirt, or dust. With all of the different types of building materials that the sealant must adhere to (e.g., metal, aluminum, PVC, steel, masonry, glass, plastics, etc.) its durability will be tested on a daily basis. Keep in mind that the daily expansion/contraction cycle of a metal roof will wear on this sealant over time as well, so if the sealant gets worn or loses flexibility, it can become vulnerable to water leaks.

3. Worn Vent Pipe Flashing 

The typical home rooftop will have a handful of various pipes sticking out of it for the purpose of providing ventilation for the HVAC system, plumbing, and the like. If the openings surrounding these pipes are not sealed tightly, they can be an easy target for rainwater, and this is what vent pipe flashing is designed to prevent. Most vent pipe flashings are comprised of a type of rubber material that almost looks like a wad of chewing gum surrounding the area where the pipes meet the rooftop. This provides a waterproof seal, but it can become worn over time due to a couple of factors: For one, metal tends to expand and contract based on changing temperatures, and this can push and pull on the seal, eventually loosening it up. Secondly, the rubber material that the vent pipe flashing is made of can become degraded due to sun exposure, requiring more and more sealant and caulking to keep it intact. This can create additional water retention on the roof, eventually causing a leak.

4. Leaky Flashing around Chimneys and Skylights 

Roof penetrations such as chimneys and skylights also require flashing to protect those vulnerable areas where the roof meets the penetrating structure. This flashing is usually made of thin metal, and can become loose, warped or worn over time, especially if it was not properly installed to begin with. Once this protective flashing has been adversely affected, water leaks tend to follow.

As you can see, there are several potential factors that can cause your metal roof to leak. If you’re currently dealing with a troublesome leak (or two) in your metal roof, give the roofing experts at Chinook Roofing and Gutters a call. We have extensive experience in metal roofing repair and installation, and we can deliver top-quality results for affordable prices. If you’re tired of worrying about that leaky metal roof, give us a call today!


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